Well, after a coupke hours of frigging with the clutch motor, I gave up and ordered a servo motor.
I tried messing with the clutch, longer clutch arms, resistance under the pedal, etc.
I could just about get it to slowly “thunk thunk”, but never reliably and I never knew when it was going to just grab and scream up to max rpm.
Its just too finicky and unreliable, especially if I plan to do upholstery leather.
oh well, at least I got to mess with it for a while. Maybe I can use that great big ac motor on a power tool somewhere....